Commercial boilers generally have multiple drums or heads (collectively, “drums”) interconnected with numerous steel boiler tubes in the range of 1-5 inches in diameter. As shown in FIG. 1, an end 1 of a boiler tube 2 is inserted through an opening 3 in a boiler drum 4 (represented here by a section of boiler drum) so that the end 1 extends into the boiler drum 4.
Boiler tubes are routinely replaced for repair or maintenance. Boiler tube removal has been achieved in the prior art by cutting the tube close to the exterior periphery of the drum opening and then notching the remaining boiler tube stub with a torch and mechanically forcing the stub out of the opening in the drum into the drum. This often leads to damage to the opening in the drum.
Other techniques in the prior art for removing boiler tube stubs include using a special tool to slit the stub through its entire length, as described in U.S. Pat. No. 5,974,642. This technique requires expensive special purpose cutting tools.
Still another technique, as described in U.S. Pat. No. 7,093,360, involves a piloted rotary cutting tool that is inserted in the stub and used to remove all but a thin shell of the stub. As shown in FIG. 2, the remaining thin shell 11 of the stub 12 is then manually peeled away from the periphery of the opening 13 in the drum 14 by a collapsing tool 15. This technique is time consuming and may score the periphery of the opening 13 in the drum 14.